WO1988003159A1 - Water-dilutable compositions for the manufacture of heat-setting coatings - Google Patents

Abstract

In the compositions described, the binder consists at least in part of a water-dilutable and at least partly epoxy-resin modified polyester. Said compositions are characterized in that the said polyester is produced (a) by synthesizing a polyester from (a1?) at least one polycarboxylic acid containing at least three carboxyl groups or a reactive derivative of this acid and/or (a2?) at least one polyol containing at least one carboxyl group and (a3?) at least one polycarboxylic acid containing two carboxyl groups or from a reactive derivative of this acid and (a4?) at least one polyol, - at least 10 moles %, preferably 30-70 moles %, of the components employed (a1?, a2?, a3?), a4?) (related to (a1?) + (a2?) + (a3?) + (a4?) = 100 moles %) comprising at least 6 carbon atoms; this polyester has a mean molecular weight (numerical mean) of less than 2000, preferably between 500 and 1500, an acidity index of between 35 and 240, preferably between 50 and 120, an OH index of between 56 and 320, preferably between 80 and 200, and all the components (a1?) and (a3?) are condensed by means of at least two carboxyl groups. (B) The polyester thus obtained is made to react with 0.3 to 1.5, preferably 0.5 to 1.0 equivalent per molecule of polyester of an epoxy-resin, having an equivalent epoxy weight of between 170 and 1000, preferably between 170 and 500, based on a biphenol, preferably biphenol A, and/or with a derivative of this epoxy-resin, containing at least one epoxy group per molecule, in reaction conditions where essentially only carboxyl groups react with epoxy groups, in order to produce a polyester modified by an epoxy resin, which, after neutralization of at least a part of the free carboxyl groups, is in a water-dilutable form.

Description

 Water-dilutable coating compositions for the production of thermosetting coatings

The invention relates to water-thinnable coating compositions for the production of thermosetting coatings, the binders of which at least partially consist of an epoxy-modified, water-thinnable polyester.

In automotive serial painting, a primer is usually applied first, then a filler and finally the top coat.

In serial painting, the filler layer is applied with the aid of preferably electrostatic spraying processes. By using electrostatic spraying processes, considerable savings in material, combined with a high degree of automation, are achieved compared to other spraying processes.

For serial painting it is extremely important that the filler material has good application behavior, i.e. good sprayability in preferably electrostatic or electrostatically assisted spraying processes, favorable theological properties, good spray mist absorption and favorable drying behavior.

One of the tasks of the filler is to fill in and cover any unevenness in order to level the surface for the subsequent topcoat. This coverage of underground Structures and substrate defects must be managed without extensive grinding work being carried out on the filler layer; a requirement that can only be met if the filler material shows good flow properties.

In addition to the optical quality, important mechanical-technological properties of the coating, such as Corrosion protection and, above all, resistance to stone chips and other mechanical attacks, crucially dependent on the quality of the filler layer.

Until now, stoving enamels based on organic solvents have predominantly been used as filler materials.

5 The paint industry is made up of economic and ecological

Reasons strive to replace the solvent-containing filler materials with water-thinnable stoving lacquers.

The object of the invention is to develop water-thinnable coating compositions for the production of heat-curable coatings which show the application properties required for use in automotive serial painting and which provide coatings which are as good or even better than 25 in their properties the coatings which have been produced using conventional filler materials containing organic solvents.

This object is achieved according to the invention by water-thinnable coating compositions, the binders of which at least partially consist of an epoxy-modified, water-thinnable polyester which has been prepared by (A) from o _o o _cr (ai) at least one at least three carboxyl groups containing polycarboxylic acid or a reactive derivative of this acid and / or (a _? ) at least one polyol having at least one carboxyl group and (a ~) at least one polycarboxylic acid containing two carboxyl groups or a reactive derivative of this acid and

(a.) at least one polyol,

- At least 10 mol%, preferably 30-70 mol%, of the components used (a ..), (a ₂ ), (a ₃ ) and (a ₄ ) (based on (a _χ ) + (a _≥ ) + (a ₃ ) + (a ₄ ) = 10 ° mol%) contain at least one (cyclo) aliphatic structural element having at least six carbon atoms - a polyester has been synthesized which has an average molecular weight (number average) of less than 2000, preferably 500 to 1500, an acid number of 35 to 240, preferably 50 to 120, an OH number of 56 to -320, preferably 80 to 200, and in which all (a _.) and (a ") components over at least two carboxyl groups are condensed in and (B) this polyester obtained in this way is then used with 0.3 to 1.5, preferably 0.5 to 1.0 equivalents per polyester molecule having an epoxy equivalent weight of 170 to 1000, preferably 170 to 500 , Epoxy resin based on a bisphenol, preferably bisphenol A, and / or a De containing at least one epoxy group per molecule rivat of this epoxy resin under reaction conditions, in which essentially only carboxyl groups react with epoxy groups, has been converted to an epoxy resin-modified polyester which is present in water-dilutable form after neutralization of at least some of the free carboxyl groups.

In the preparation of the binders according to the invention, components (a ₁ ), (a ₂ ), (a ₃ ) and (a ₄ ) are to be selected in terms of type and amount such that at least 10 mol%, preferably 30 to 70 mol%, of the used Components (a ₁ ), (a ₂ ), (a ₃ ) and (a ₄ ) (based on (a ₁ > + (a _≥ ) + (a ₃ ) + (a ₄ ) = 100 mol%)) at least one (cyclo) aliphatic structural element having at least six carbon atoms contain and that according to generally known synthetic principles from the components (a ₁ ) and / or (a ₂ ), (a ₃ ) and (a ₄ ) a polyester can be synthesized which has an average molecular weight (number average) of less than 2000, preferably 500 to 1500, an acid number of 35 to 240, preferably 50 to 120, an OH number of 56 to 320, preferably 80 to 200, and in which all (a-) and (a ~) components over at least two carboxy groups are condensed.

The carboxyl groups of the polyester are supplied by components (a) and / or (a ₂ ). The polyester can be used using only the carboxyl group suppliers (a-) or (a _? ) Or using a mixture of the

Components (a_.) And (a ~) are built.

In principle, any component suitable for the production of polyesters and containing at least three carboxyl groups or a reactive derivative (for example anhydride, ester or halide) or a mixture of such acids or acid derivatives can be used as component (a ₁ ), taking into account the above-mentioned requirements become. Examples include trimellitic acid, trimesic acid (1,3,5-benzenetricarboxylic acid), pyromellitic acid and trimeric fatty acids. Trimellitic acid is preferably used.

Component (a ₂ ) can in principle be any carboxyl-containing polyol or a mixture of such polyols suitable for the production of polyesters, taking into account the above-mentioned requirements, a polyol being understood to mean an organic compound which carries at least two hydroxyl groups ¬ Dimethylolpropionic acid is used as (a ") component. As component (a, in principle, any polycarboxylic acid containing two carboxyl groups or a reactive derivative (eg anhydride, ester or halide) or a mixture of such acids or acid derivatives suitable for the preparation of polyesters or a mixture of such acids or acid derivatives can be used. As examples Suitable acids include: phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, endomethylene tetrahydrophthalic acid, succinic acid, adipic acid, corkic acid, acelainic acid, sebacic acid and dimeric fatty acids. Phthalic acid, isophthalic acid, adipic acid and dimeric acids are preferred.

Component (a ₄ ) can in principle be any polyol or a mixture of polyols suitable for the production of polyesters, taking into account the above-mentioned requirements, polyol being understood as an organic compound which carries at least 2 hydroxyl groups. Suitable polyols are, for example, ethylene glycol, propanediols, butanediols, pentanediols, neopentyl glycol, hexanediols, diethylene glycol, glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, hydroxypivalic acid neopentylglycol ester, 2-methyl-2-propyl, propyl-2-propyl 2,2,4-trimethylpentanediol-1, 3 and 2,2,5-trimethylhexanediol-1,6. Neopentyl glycol, 1,6-hexanediol and hydroxypivalic acid neopentyl glycol esters are preferably used.

The polyester produced from components (a.) And / or (a ₂ ), (a ₃ ) and (a ₄ ) with the above-mentioned characteristics is 0.3 to 1.5, preferably 0.5 to 1.0 equivalents per polyester molecule of an epoxy resin having an epoxy equivalent weight of 170 to 1000, preferably 170 to 500, epoxy resin based on a bisphenol, preferably bisphenol A, and / or a derivative of this epoxy resin containing at least one epoxy group per molecule under reaction conditions in which essentially only Carboxyl groups react with epoxy groups to form an inventive one implemented epoxy resin-modified polyester which, after neutralization of at least some of the free carboxyl groups, is present in water-dilutable form.

The epoxy resins based on a bisphenol, preferably bisphenol A, are generally reaction products of bisphenols with epichlorohydrin. These epoxy resins should have an epoxy equivalent weight of 170 to 1000, preferably 170 to 500, and preferably contain on average one to two, particularly preferably two, epoxy groups per molecule.

It is also possible to use at least one epoxy group-containing derivative of these epoxy resins. Suitable derivatives can be at least one epoxide group per molecule having reaction products of the above-mentioned epoxy resins and a (cyclo) aliphatic mono- or polycarboxylic acid, preferably a mono- or polycarboxylic acid with a (cyclo) aliphatic having at least 6 carbon atoms Structural element can be used. The derivatives can be prepared by reacting the epoxy resins in question, for example, with polymeric, preferably dimeric, fatty acids, adipic acid, azelaic acid, dodecanedicarboxylic acid, long-chain monocarboxylic acids, tetrahydrophthalic acid or hexahydrophthalic acid in such a way that reaction products are formed which still contain at least one Contain epoxy group per molecule.

Very particularly preferred water-dilutable coating compositions are obtained if the polyester synthesized in step (A) contains 0.3 to 1.5, preferably 0.5 to 1.0 equivalents per polyester molecule of a reaction product having at least one epoxy group per molecule product of an epoxy resin based on a bisphenol, preferably bisphenol A, with an epoxy equivalent weight of 170 to 1000, preferably 170 to 500, and a (cyclo-) aliphatic mono- or polycarboxylic acid with an independent at least 18 carbon atoms (cyclo) aliphatic structural element, preferably a polymeric, in particular a dimeric, fatty acid.

The reaction between the polyester synthesized in step (A) with the epoxy resin or epoxy resin derivative must be carried out in such a way that essentially only the carboxyl groups of the polyester are reacted with the epoxy groups of the epoxy resin and that competitive reactions, such as e.g. The reaction of hydroxyl groups with epoxy groups only take place to a minor extent.

Suitable reaction conditions include: reaction temperature 25-180 C, preferably 80-160 C. The reaction can be carried out in an internal solvent or in bulk and is advantageously carried out using basic catalysts, such as e.g. tertiary amines, catalyzed.

After neutralization of at least some of the carboxyl groups contained in the epoxy resin-modified polyester according to the invention with basic compounds, such as e.g. Ammonia, aliphatic secondary and tertiary amines, such as diisopropanol in, dimethyl and diethylaminoethanol and trimethyl, triethyl and tripropylamine, preferably tertiary amines, the epoxy resin-modified polyester according to the invention is in water-dilutable form.

Epoxy resin-modified polyesters of the invention, crosslinkers are tongues for preparing the Überzugszusammenset- invention (for example, amino resins, ^{'particularly} those of the type hexamethoxymethylmelamine, urea resins, epoxy resins wasserver¬ dilutable udgl.), Optionally further binders, pigments, fillers and other customary additives to a water-dilutable Processed coating composition.

In addition to water, the water-dilutable coating compositions according to the invention can also be used in subordinate Dimensions contain solvent as a diluent.

A great advantage of the polyesters according to the invention is their good compatibility with the other coating components, in particular with crosslinking agents and other binders which may be present in the coating composition.

In an advantageous embodiment, the coating compositions according to the invention contain the polyester according to the invention as the sole binder; this embodiment is made possible by the fact that the polyester according to the invention can also be used as a rubbing resin due to its excellent pigment wetting properties.

The coating compositions according to the invention show excellent application properties even in the case of fluctuating air humidity values and are well suited for use in series coating. They can be processed particularly well with electrostatic or electrostatically assisted spraying processes, show favorable theological properties, good spray mist absorption, good flow properties, favorable drying behavior and good wetting behavior compared to PVC.

The baked layers obtained with the aid of the coating compositions according to the invention, in addition to having a good corrosion protection effect, show a lower tendency to yellowing and optimum intermediate adhesion properties in comparison with known systems. Together with the primer and the topcoat layer or layers, they lead to coatings with a very good Topcoat level and excellent resistance to stone chips and other mechanical attacks, even at very high and very low temperatures.

The possible uses of the coating compositions according to the invention are not for automotive coatings limited. They can also be used for the single- or multi-layer coating of any other substrates. Suitable substrates can, for example, be made of ceramic, glass, concrete, plastic, preferably metal such as iron, zinc, copper, aluminum, steel and the like. consist.

With the coating compositions according to the invention, coatings can be obtained which have a particularly high gloss.

In addition, the coating compositions according to the invention provide coatings which adhere excellently to the optionally pretreated substrates and show very good resistance values to mechanical attacks and organic solvents.

The invention is explained in more detail in the following examples. All information on parts and percentages are by weight unless expressly stated otherwise.

Representation of an epoxy resin-modified, water-dilutable polyester (polyester A)

442.4 g of 1,6-hexanediol and 166.6 g of a technical polymeric fatty acid (dimer content at least 80% by weight, triene content at most 20% by weight, monomer content at most 1% by weight) are combined in one using heat transfer oil heatable stainless steel reaction vessel, which is provided with an anchor stirrer, packed column, vapor condenser with receiver, protective gas feed line (N ") and temperature sensors for the temperature of the reaction mixture and the vapor temperature at the top of the column, weighed and heated to 130.degree. Then 184.3 g of isophthalic acid are added and the mixture is heated further. As soon as condensation water forms (from around 160 C), the temperature of the reaction mixture is increased so slowly while distilling off the condensation water up to a maximum of 220 ° C that the vapor temperature at the top of the column does not exceed 103 ° C. increases. It is condensed at 220 C until the reaction material has reached an acid number of 10.5. After cooling to 140 ° C., 266.7 g of trimellitic anhydride are added in portions to the reaction mixture with stirring. The mixture is then heated to 150 ° C. and esterified until the reaction mixture has reached an acid number of 67.7. The mixture is then cooled to 120 ° C. and diluted with ethylene glycol monobutyl ether in such a way that a solution with a solids content of 85% by weight (determined after drying at 130 ° C. in a circulating air drying cabinet for 60 minutes) is obtained. A P Prroobbee diluted to 50% by weight with ethylene glycol monobutyl ether at the same time has an amount of 420 mPa's (23 C ICI plate-cone viscometer)

The 85% polyester solution is heated to 140 ° C. and 209.6 g of an epoxy resin composed of bisphenol-A and epichlorohydrin with an epoxy equivalent weight of 490 are added in portions with stirring. The reaction is then continued at 140 ° C. until an epoxy equivalent weight of more than 50,000 and an acid number of 42.1 (based on solids) have been reached. It is then cooled to 100 ° C. and neutralized with 64.6 g of N, N-dimethylethanolamine. The reaction mixture is then discharged with stirring into 2,000 g of deionized water which has been heated to 60 ° C., and a stable binder dispersion is produced by intensive stirring, which is applied to a solid with 180 g of deionized water and N, N-dimethylethanolamine of 35% by weight (determined after drying for 60 minutes at 130 ° C in a forced-air drying cabinet) and a pressure at 23 ° C of 6.67. »

Representation of an epoxy resin-modified, water-dilutable polyester (polyester B)

In the apparatus described for the preparation of polyester A, in which the packed column and the vapor condenser were replaced by a reflux condenser Weighed in 922.5 g of an epoxy resin composed of bisphenol-A and epichlorohydrin with an epoxy equivalent weight of 185 and 2.5 g of N, N-dimethylbenzylamine and heated to 100 ° C. with stirring. Then 600.0 g of the polymeric fatty acid used to prepare polyester A are added in portions at 100 ° C. and heated to 140 ° C. The reaction is continued until an acid number of 1.5 and an epoxy equivalent weight of 535 has been reached. The mixture is then diluted with 380 g of diethylene glycol monobutyl ether. (A 50% by weight solution of the product in diethylene glycol monobutyl ether shows a solution viscosity of 120 mPa ^* s (23 ° C., ICI plate-cone viscometer.)

From the polyester produced in the first stage of the preparation of polyester A, 1,110 g of a 90% by weight solution in ethylene glycol monobutyl ether are prepared and mixed with 270 g of the epoxy resin solution prepared by the process described above. The mixture is on

Heated 140 ° C and reacted at 1 ^ 0 ° C until the product has an acid number of 40.9 (based on solids) and an epoxy equivalent weight of more than 50,000. The reaction mixture is then cooled to 100 ° C., neutralized with 63.0 g of N, N-dimethylethanolamine and, analogously to the preparation of polyester A, converted into an aqueous dispersion with a solids content of 35% by weight and a pH of 6.60.

Production of some coating compositions according to the invention

Deionized water and N, N-dimethylethanolamine are added to the aqueous polyester dispersions obtained in accordance with the above-described regulations, in accordance with the weight ratios given in Table 1, pasted with post-treated titanium dioxide of the rutile type and mixed with an unsaturated branched diol as an anti-foaming agent. These mixtures are filled in a discontinuous laboratory sand mill and dispersed until a fineness by Max. 10 µm, measured in a Hegmann grindometer, is achieved. The coating compositions 1, 2, 3 and 4 according to the invention are then obtained from the dispersing mixtures with the addition of further polyester dispersion, low molecular weight melamine resin, highly etherified with methanol, ethylene glycol ethers, water-dilutable acrylate resin as leveling agent and deionized water (cf. Table 1).

Application on phosphated steel sheets

The coating compositions prepared in accordance with the above-described regulations were adjusted to a viscosity of 25 s with deionized water, measured in a discharge cup according to DIN 4 at 20 ° C., and in with a flow cup gun (nozzle opening 1.2 mm; air pressure 4.5 bar) two cloisters with 1 minute flash-off time sprayed onto phosphated steel sheets. The application was carried out at an air temperature of 23 C and a relative humidity of 60%. The sprayed panels were flashed off in a forced air oven for 10 minutes at 23 ° C. and 10 minutes at 80 ° C. and then baked in a forced air oven for 20 minutes at 160 ° C., cooled and assessed.

The coating compositions prepared according to the above-described regulations were also applied electrostatically. An Esta-Behr system with a bell TOS 300/5/8, a distance of 30 cm and a speed of 30,000 revolutions per minute was used at a relative humidity of 40-70%.

Although no special conditioning of the spray booth was carried out, coatings with a high gloss and very good flow were obtained both with thin (approx. 30 μm) and with thicker layer thicknesses (approx. 54 μm). The coatings showed excellent elasticity, good adhesion, high resistance to yellowing and good PVC wetting behavior (cf. Table 2). Application of the coating compositions according to the invention to steel sheets coated with an electrocoat

The coating compositions 1 to 4 according to the invention were sprayed onto the phosphated steel sheets coated with an electrodeposition paint according to Example 6 of DE-0S-2701002 by the process set out above. The coatings obtained showed a very good flow, covered the structure of the electrocoating very well and showed good intermediate adhesion to the electrocoating primer (cf. Table 3).

Application of the coating compositions according to the invention as a filler

The coating compositions of the invention were applied to baked steel sheets as described above and baked. After cooling, the panels were then additionally coated with a solvent-based white baking topcoat based on an alkyd resin with saturated and unsaturated fatty acids (acid number 12, OH number 110) in combination with a medium molecular weight melamine resin, partially etherified with n-butanol (ratio 2: 1), pigmented with a post-treated titanium dioxide of the rutile type (PVC 21%) and with solvents and additives, which are usually used for the processing of a paint for automotive serial painting, sprayed over and baked at 130 C for 30 min (dry film thickness

37 to 40 µm).

The coatings are characterized by good flow, good coverage of the structure of the primer and good intermediate adhesion (cf. Tab. 4). Table 1

Coating composition 1 2 3 4

Polyester A 20.0 20.0 - ..- it.

Polyester B - - 20.0 ^'20 .0 deionized water 5.8 5.8 5.8 5.8

N, -Dimethylethanolamine 0.1 0.1 0.1 0.1

Titanium dioxide 20.0 20.0 20.0 20.0

Antifoam (50% solution in ethylene glycol monobutyl ether) 0.3 0.3 0.3 0.3

Dispersing mixture 46.2 46.2 46.2 46.2

Polyester A 44.3 37.1 -

Polyester B - - 44.3 37.1

Melamine resin (100%) 2.6 5.1 2.6 5.1

Diethylene glycol monobutyl ether 3.0 3.0 3.0 3.0 Ethylene glycol monobutyl ether 2 2.00 00 2.0 2.0 2.0

Leveling agent (50% solution in ethylene glycol monobutyl ether) 1.0 1.0 1.0 1.0 deionized water 0.9 5.6 0.9 5.6 100.0 100.0 100.0 100.0

(all figures in% by weight)

Table 2

Coating composition 1 2 3 4

Layer thickness (, um) 41 45 45 45

Cross cut according to DIN 53151 (Gt B) Gt 2 Gt 1-2 Gt 2 Gt 2

Erichsen depression 8.5 7.1 8.7 ^' 7.5

Gloss (Gardner 60 °) 94 96 94 92 Buchholz hardness 91 118 91 105

Yellowing 3h / 160 ° C 0 0 0-1 0

PVC wetting *

Intercol 0787 1 1 1 1

Togol 1 1 1-2 1 Unitecta 1-2 1 2 2

* Grading scale 0 (very good) to 5 (very bad)

Table 3

Coating composition

Layer thickness (, um) 41 45 45 45

Cross cut according to DIN 53151

(Gt B) Gt 0-1 Gt 1 Gt 0-1 Gt 1

Buchholz hardness 91 105 100 105

Erichsen depression 6.7 5.8 6.9 6.2

Gloss (Gardner 60 °) 96 97 94 94 Table 4

Coating composition

Layer thickness of the filler (, um) 40 43 46 45

Cross cut according to DIN 53151 (Gt B) Gt 1 Gt 2-3 Gt 1-2 Gt 1-2

Erichsen depression 6.2 5.8 6.0 5.8

Stone chip test 3 3-4 2-3 3

The stone chip test was carried out with a VDA stone chip testing device (model 508) (one-off bombardment within 20 s with 1000 g of steel shot; pressure 2 bar). The rating scale ranges from 1 (very good) to 10 (very bad).

Claims

Claims 1. Water-dilutable coating compositions for the production of thermosetting coatings, the binders of which at least partially consist of an epoxy-modified, water-dilutable polyester, characterized in that the epoxy-modified, water-dilutable polyester has been prepared by (A) from (a) at least an at least three carboxyl group-containing polycarboxylic acid or a reactive derivative of this acid and / or (a _? ) at least one polyol having at least one carboxyl group and (a_) at least one polycarboxylic acid containing two carboxyl groups or a reactive derivative of this acid and (a ₄ ) at least a polyol, - At least 10 mol%, preferably 30-70 mol%, of the components (a.), (a "), (a") and (a ₄ ) used (based on (a _χ ) + (a ₂ ) + ( a ₃ ) + (a ₄ ) = 100 mol%) contain at least one (cyclo) aliphatic structural element having at least six carbon atoms - a polyester has been synthesized which has an average molecular weight (number average) of less than 2000, preferably 500 to 1500, an acid number of 35-240, preferably 50-120, an OH number of 56-320, preferably 80-200, and in which all (a _χ ) and (a ₃ ) components have at least two carboxyl groups are encoded and (B) this polyester obtained in this way subsequently with 0.2 to 1.5, preferably 0.5 to 1.0 equivalents per polyester molecule of an epoxy resin based on a bisphenol and having an epoxy equivalent weight of 170 to 1000, preferably 170 to 500, preferably bisphenol A, and / or a derivative of this epoxy resin containing at least one epoxy group per molecule under reaction conditions in which essentially only carboxyl groups react with epoxy groups, has been converted to an epoxy resin-modified polyester which, after neutralization of at least some of the free carboxyl groups, is diluted in water - presentable form. 2. Water-dilutable coating compositions according to claim 1, characterized in that some of the components (a.) And / or (a ") consisted of at least one polymeric, preferably dimeric fatty acid. Water-dilutable coating compositions according to claim 1 or 2, characterized in that the polyester obtained in step (A) with 0.3 to 1.5, preferably 0.5 to 1.0 equivalents per polyester molecule of a reaction product having at least one epoxy group per molecule from an epoxy resin based on a bisphenol, preferably bisphenol A, with an epoxy equivalent weight of 170 to 1000, preferably 170 to 500, and a (cyclo) aliphatic mono- or polycarboxylic acid, preferably a mono- or polycarbonate acid with an at least 6 C. -Atomic (cyclo-) aliphatic structural element has been implemented. Water-dilutable coating compositions according to one of claims 1 to 3, characterized in that the polyester obtained in step (A) with 0.3 to 1.5, preferably 0.5 to 1.0 equivalents per polyester molecule of at least one epoxy group per molecule comprising reaction product of an epoxy resin based on a bisphenol, preferably bisphenol A, with an epoxy equivalent weight of 170 to 1000, preferably 170 to 500, and a (cyclo) aliphatic mono- or polycarboxylic acid having at least 18 carbon atoms (cyclo -) Aliphatic structural element, preferably a poly eren, especially a dimeric fatty acid, has been implemented.